1. Field of the Invention
The invention relates generally to building maps of traffic signals. More specifically, these maps may be used to perform real time traffic signal detection.
2. Description of Related Art
A key component of a robot vehicle is the perception system, which allows the vehicle to perceive and interpret its surroundings while driving. Humans have engineered the driving problem to make it easier. For example, lanes are delineated by lines painted on the road, traffic lights for precedence at intersections, brake lights, and turn signals, are all intended to simplify the perception task. Robots can use these driving aids, but in many cases they are able to use alternative sensing modalities, such as radar or lidar, instead of vision. In addition to these other sensing modalities, robots can often leverage prior maps to simplify online perception. Using a prior map that includes stop signs, speed limits, lanes, etc., a robot vehicle can largely simplify its onboard perception requirements to the problem of estimating its position with respect to the map (localization), and dealing with dynamic obstacles, such as other vehicles (perception).
Traffic signals are a major challenge for robot vehicles. Efforts have been made to broadcast traffic light state over radio, but this requires a significant investment in infrastructure. While robots can often employ active sensors such as radar and lidar to perceive their surroundings, the state of traffic signals can only be perceived visually. Although any vision task may be challenging due to the variety of outdoor conditions, traffic lights have been engineered to be highly visible.